Receiver diversity in a communication system

ABSTRACT

A communication system is described. In one embodiment, the communication system comprises a mobile station having a transmitter to transmit packets wirelessly according to a protocol and multiple repeaters communicably coupled with the mobile station. Each of the plurality of repeaters receives one or more packets of the wirelessly transmitted packets from the mobile station. Each of the repeaters receives an indication of which of the wirelessly transmitted packets were received without errors by other repeaters and a received signal strength for those packets. The communication system also includes a switch coupled to the repeaters. Each of the repeaters forwards to the switch each packet of the wirelessly transmitted packets that each repeater had received without errors at a received signal strength higher than any other repeater.

FIELD OF THE INVENTION

The present invention relates to the field of wireless communications;more particularly, the present invention relates to receiver diversityin a wireless communications system.

BACKGROUND OF THE INVENTION

FIG. 1 illustrates an exemplary network environment used today.Referring to FIG. 1, a corporate Local Area Network (LAN) backbone 102interfaces to a number of desktop computers 103 ₁-103 _(n) and mayinterface to Internet 101. Corporate LAN backbone 102 may comprise afirewall 102A, corporate server 102B, and a standard Ethernet switch102C. Ethernet switch 102C includes an interface by which desktops 103₁-103 _(1n) are coupled to the corporate LAN backbone 102 and may accesscorporate sever 102B and Internet 101 (via firewall 102A).

More recently, Wireless LANs (WLANs) are being installed. Many of therecently implemented WLANs operate according to the protocol set forthin the 802.11 Standard, particularly as more enterprises are adoptingthe 802.11 Standard. ISO|IEC DIS 8802.11.

FIG. 2 illustrates one embodiment of an 802.11 based WLAN (LAN) system.Referring to FIG. 2, the Internet or other LAN 201 is coupled to an802.11 server 203 via firewall (FW) 202. Server 203 communicates withmobile stations in a number of 802.11 cells 206 ₁-206 _(n) using anaccess point in each of cells 206 ₁-206 _(n), such as access point 204.Server 203 is coupled to access points such as access point 204, via anEthernet connection. There is one access point for each of the 802.11cells 206 ₁-206 _(n). Mobile stations in each of the 802.11 cells, suchas laptops 205 ₁ and 205 ₂ in cell 206 ₁, communicate wirelessly withthe access points via the 802.11 protocol. The communications frommobile stations in the 802.11 cells to the access points are forwardedthrough to server 203 and potentially to Internet/LAN 201, whilecommunications from Internet/LAN 201 are forwarded through server 203 tothe mobile stations via the access points.

There are a number of problems associated with the currentimplementations of 802.11 networks. For example, in order to set up an802.11 network such as shown in FIG. 2, a site survey is required inorder to determine where each of the access points are placed to ensurethat the 802.11 cells provide complete coverage over a particulargeographic area. This may be costly. Also, the cost of each of theaccess points is approximately $500.00. Generally, such a high cost is adeterrent to having a large number of access points. However, byreducing the number of access points, coverage diminishes and the 802.11network is less effective. Furthermore, there are a number of mobilityproblems associated with the current 802.11 network deployments. Forexample, the 802.11 standard sets forth a number of solutions to handlethe issue of mobility of mobile stations between the 802.11 cells.However, these schemes do not work effectively as there is no standardsolution in place and users haven't indicated a desire for long-termproprietary solutions.

SUMMARY OF THE INVENTION

A communication system is described. In one embodiment, thecommunication system comprises a mobile station having a transmitter totransmit packets wirelessly according to a protocol and multiplerepeaters communicably coupled with the mobile station. Each of theplurality of repeaters receives one or more packets of the wirelesslytransmitted packets from the mobile station. Each of the repeatersreceives an indication of which of the wirelessly transmitted packetswere received without errors by other repeaters and a received signalstrength for those packets. Each of the repeaters sends anacknowledgement packet to the mobile device for packets received at ahigher received signal strength than any other repeater. Thecommunication system also includes a switch coupled to the repeaters.Each repeater forwards to the switch wirelessly transmitted packets.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given below and from the accompanying drawings of variousembodiments of the invention, which, however, should not be taken tolimit the invention to the specific embodiments, but are for explanationand understanding only.

FIG. 1 illustrates an exemplary network environment used today.

FIG. 2 illustrates one embodiment of an 802.11 based wireless LAN-based(LAN) system.

FIG. 3 illustrates one embodiment of a network architecture.

FIG. 4A is a flow diagram of one embodiment of a receiver diversityprocessing performed by a repeater.

FIG. 4B is a flow diagram of one embodiment of a receiver diversityprocessing performed by a switch.

FIG. 4C is a process for managing repeaters using a token-basedmechanism.

FIG. 4D is one embodiment of a token-based process for handling packets.

FIG. 5A illustrates one technique for location tracking by RSSI.

FIG. 5B is a flow diagram of one embodiment of a process for performinglocation tracking by a switch.

FIG. 6 illustrates mobility supported by routing.

FIG. 7 illustrates one embodiment of a network system.

FIG. 8 illustrates one embodiment of a protocol architecture.

FIG. 9A illustrates one embodiment of a rotation tracking system.

FIG. 9B illustrates one embodiment of a repeater.

FIG. 10 illustrates one embodiment of a hardware architecture for arepeater.

FIG. 11 is a block diagram of one embodiment of the base stand processorof a repeater.

FIG. 12 is a block diagram of one embodiment of a switch.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

A communication system is described. In one embodiment, thecommunication system comprises a mobile station having a transmitter totransmit packets wirelessly according to a protocol and multiplerepeaters communicably coupled with the mobile station. Each of theplurality of repeaters receives one or more packets of the wirelesslytransmitted packets from the mobile station. Each of the repeatersreceives an indication of which of the wirelessly transmitted packetswere received without errors by other repeaters and a received signalstrength for those packets. The communication system also includes aswitch coupled to the repeaters. Each of the repeaters forwards to theswitch each packet of the wirelessly transmitted packets that eachrepeater had received at a received signal strength higher than anyother repeater.

In the following description, numerous details are set forth in order toprovide a thorough understanding of the present invention. It will beapparent, however, to one skilled in the art, that the present inventionmay be practiced without these specific details. In other instances,well-known structures and devices are shown in block diagram form,rather than in detail, in order to avoid obscuring the presentinvention.

Some portions of the detailed descriptions which follow are presented interms of algorithms and symbolic representations of operations on databits within a computer memory. These algorithmic descriptions andrepresentations are the means used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of steps leading to a desiredresult. The steps are those requiring physical manipulations of physicalquantities. Usually, though not necessarily, these quantities take theform of electrical or magnetic signals capable of being stored,transferred, combined, compared, and otherwise manipulated. It hasproven convenient at times, principally for reasons of common usage, torefer to these signals as bits, values, elements, symbols, characters,terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the following discussion,it is appreciated that throughout the description, discussions utilizingterms such as “processing” or “computing” or “calculating” or“determining” or “displaying” or the like, refer to the action andprocesses of a computer system, or similar electronic computing device,that manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission or display devices.

The present invention also relates to apparatus for performing theoperations herein. This apparatus may be specially constructed for therequired purposes, or it may comprise a general purpose computerselectively activated or reconfigured by a computer program stored inthe computer. Such a computer program may be stored in a computerreadable storage medium, such as, but is not limited to, any type ofdisk including floppy disks, optical disks, CD-ROMs, andmagnetic-optical disks, read-only memories (ROMs), random accessmemories (RAMs), EPROMs, EEPROMS, magnetic or optical cards, or any typeof media suitable for storing electronic instructions, and each coupledto a computer system bus.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct more specializedapparatus to perform the required method steps. The required structurefor a variety of these systems will appear from the description below.In addition, the present invention is not described with reference toany particular programming language. It will be appreciated that avariety of programming languages may be used to implement the teachingsof the invention as described herein.

A machine-readable medium includes any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputer). For example, a machine-readable medium includes read onlymemory (“ROM”); random access memory (“RAM”); magnetic disk storagemedia; optical storage media; flash memory devices; electrical, optical,acoustical or other form of propagated signals (e.g., carrier waves,infrared signals, digital signals, etc.); etc.

Exemplary Network Architecture

FIG. 3 illustrates one embodiment of a network architecture. Referringto FIG. 3, a LAN backbone 102 interfaces a number of desktops 103 ₁-103_(n) to Internet 101. Note that the present invention does not requirethat a LAN backbone be included. All that is necessary is that there bea communication mechanism that is capable of receiving packets fromother devices and/or sending packets to other devices.

Similar to FIG. 1, LAN backbone 102 includes firewall 102A, corporateserver 102B and Ethernet switch 102C. However, in contrast to FIG. 1,LAN backbone 102 also includes switch 301 which interfaces to repeaters302 ₁-302 ₃. Although only three repeaters are shown, alternativeembodiments may utilize any number of repeaters with a minimum of one.In one embodiment, switch 301 is coupled to repeaters 302 ₁-302 ₃ via awired connection, such as cabling. In one embodiment, the wiredconnection may comprise CAT5 cabling.

Each of the repeaters 302 ₁-302 ₃ receives wireless communications fromdevices (e.g., mobile stations such as, for example, a mobile phone, acellular phone, a cordless phone, a headset, a voice-enabled mobilestation, a laptop computer system, a personal digital assistant, acomputer-data-enabled mobile station, a speakerphone, video gamecontroller, a DVD controller, a stereo controller, a TV controller,etc.) in the coverage areas of the repeaters. In one embodiment, thesewireless communications are performed according to the 802.11 protocol.That is, each of the mobile stations in each of cells 310 ₁-310 _(n)exchanges packets with the repeaters 302 ₁-302 ₃ using the 802.11protocol.

In one embodiment, switch 301 includes 802.11 MAC protocol software thatallows switch 301 to communicate with repeaters 302 ₁-302 ₃. Differentfrom the prior art, many of the 802.11 MAC functionality typicallyassociated with the access points, as described above in the Backgroundsection, are taken out of the repeaters 302 ₁-302 _(n) and centralizedin switch 301. More specifically, the MAC layer is split to enabletransfer of messages over wiring (e.g., CAT5 cabling). As such,repeaters 302 ₁-302 ₃ and switch 301 are interfaced at the inside the802.11 MAC layer as described below.

In one embodiment, switch 301 includes one or more Ethernet connectors(e.g., external Ethernet connector) so that a computer system, such asdesktop computer system 303, or other device, has an Ethernet connectionto LAN backbone 102 via switch 301. Similarly, in one embodiment, one ormore of repeaters 302 ₁-302 ₃ includes an Ethernet connector to enable adevice (e.g., computer system, such as desktop computer system 304) togain access, via a repeater, such as repeater 302 ₃, to switch 301 andthe rest of the communication system. In such a case, the wiringcoupling switch 301 to repeaters 302 ₁-302 ₃ may combine 802.11information including management and control (as opposed to solely data)information with traditional Ethernet packets on the same wiring (e.g.,CAT5).

Distributed Receiver Diversity Approach

The network architecture described above allows for overlapping coveragebetween cells supported by the repeaters. This overlapping coverageallows for receiver diversity.

The packets from the mobile stations in each of the cells are broadcastand may be received by multiple repeaters. By allowing multiplerepeaters to receive packets from one of the mobile stations, collisionsand dropped packets may be reduced or avoided. For example, if acollision occurs or if a packet is dropped by one of the repeaters, thena particular packet can still be received by other repeaters. In thismanner, the use of repeaters described herein provides for higherreliability.

In an embodiment in which mobile stations exchange packets withrepeaters using the 802.11 protocol, each packet from a mobile stationincludes an Ethernet MAC address, which is embedded in the packet. Eachpacket may be received by one or more repeaters. Each repeater thatreceives a packet from a mobile station without errors (i.e., cleanly)determines the received signal strength of the packet in a mannerwell-known in the art. The received signal strength is converted into anindication, such as a received signal strength indicator (RSSI). Therepeater forwards the packet, along with the RSSI. In one embodiment,the repeater encapsulates the packet into an Ethernet packet with theRSSI in a header and forwards the Ethernet packet to switch 301. In oneembodiment, the RSSI is specified in a value from 1 to 127. These 128discrete values can be mapped to dB signal strength values based on theparticular implementation being used. Thus, all packets received frommobile stations by a repeater without errors are forwarded to switch301. Switch 301 knows which repeater sent the packet(s) because it isreceived on its preassigned port.

In one embodiment, the fact that a particular repeater received a packetwithout errors is communicated to all other repeaters. In oneembodiment, this is accomplished by having the repeater send eachencapsulated packet and its RSSI as a broadcast packet to switch 301.This broadcast packet is similar to those broadcast packets used inEthernet and includes a special broadcast address, which is recognizedby switch 301. In another embodiment, only the header of the packet,which includes the RSSI and uniquely identifies the packet, isencapsulated and sent as a broadcast packet to the other repeaters. Inthis case, the data portion of the packet is not forwarded.

In response to receiving the broadcast packet with the specificbroadcast address, switch 301 broadcasts the packet on all of the otherports used for communication between switch 301 and the other repeaters.

In one embodiment, upon receiving a packet without error from aparticular mobile station, the repeater sets a timer within which it isto receive packets received by other repeaters that are duplicates tothe packet it has already received. When the timer expires, the repeaterexamines the RSSI of the packet it received (without error) with theRSSI values of duplicate packets received by other repeaters. Based onthat information, the repeater determines if it is to send theacknowledgement packet. Thus, if the time expires without receiving aduplicate packet, the repeater sends the acknowledgement. If the timerexpires and the repeater receives a duplicate packet, thereafter, it istreated as a new packet. To avoid this, the timer time out value is setto handle the worst case time delay that a repeater may face inreceiving duplicate packets.

Note that switch 301 forwards each packet received from repeaters (noteduplicates) to the rest of the communication system (e.g., LAN backbone,other mobile stations, the Internet, etc.). In one embodiment, thisoccurs after de-duplication of packets so that only one copy of eachpacket is forwarded.

Once the broadcast packets have been received, all the repeaters knowwhat packets were received cleanly by the others and at what RSSI thepackets were received by the other repeaters. Thereafter, each repeaterselects the packet with the highest RSSI and determines the repeaterthat received it. In other words, each repeater performs a comparison onthe received signal strength of the packets it received that were alsoreceived by one or more other repeaters. For each of the packets that arepeater receives at a power level higher than any of the otherrepeaters that received that packet, that repeater sends anacknowledgement back to the mobile station acknowledging that the packetwas received without errors. This prevents all the repeaters thatreceive the packet cleanly from sending multiple acknowledgements tomobile station.

In one embodiment, if two repeaters have the same receive signalstrength for a packet, the repeater with the lower port number (the portnumber by which switch 301 is coupled to the repeater) is the repeaterthat is elected to send the acknowledgement to the mobile station. Inthis manner, only one repeater is selected to send the acknowledgementto the mobile station and, thus, the receiver diversity is handled inthe network architecture in a distributed fashion. In one embodiment, toenable the repeaters to determine which is to send the acknowledgementin case of a packet received with the same received signal strength bymultiple repeaters, each packet includes identification information,such as its switch port number, to enable the determination of which hasthe lowest port number. Note, in an alternative embodiment, the repeaterwith the highest port number may be the one to send the acknowledgementor other preassigned priority information may be used by the repeatersin such situations.

FIG. 4A is a flow diagram of one embodiment of a receiver diversityprocess performed by a repeater. The process is performed by processinglogic that may comprise hardware (circuitry, dedicated logic, etc.),software (such as is run on a general purpose computer system or adedicated machine), or a combination of both.

Referring to FIG. 4A, processing logic initially receives a 802.11packet (processing block 401). In response to the 802.11 packet,processing logic determines the received signal strength (e.g., RSSI)(processing block 402). In one embodiment, this processing logiccomprises a hardware mechanism, such as a radio frequency (RF) device(e.g., integrated circuit (e.g., RF IC 1002 in FIG. 10)) in therepeater. In such a case, the RF device sends the RSSI to a basebandprocessor in the repeater.

Thereafter, processing logic encapsulates 802.11 packet and RSSI in anEthernet packet (processing block 403) and sends the Ethernet packet tothe switch (processing block 404). In one embodiment, a basebandprocessor (e.g., baseband processor 1001 in FIG. 10) performs theencapsulation and sends the Ethernet packet to the switch.

Later in time, processing logic receives one or more packets from theswitch that are duplicates of the 802.11 packet. These duplicate packetsare transmitted by other repeaters and encapsulated by those repeaters,along with their RSSIs (processing block 405). Processing logic in therepeater compares RSSIs for the duplicate packets (processing block406). In one embodiment, a baseband processor (e.g., baseband processor1001 in FIG. 10) performs the comparison. If the repeater determines itreceived the 802.11 packet with the highest RSSI, then processing logicsends the acknowledgment packet to the mobile station (processing block407).

FIG. 4B is a flow diagram of one embodiment of a receiver diversityprocessing performed by a switch. The process is performed by processinglogic that may comprise hardware (circuitry, dedicated logic, etc.),software (such as is run on a general purpose computer system or adedicated machine), or a combination of both.

Referring to FIG. 4B, processing logic initially receives a packet froma repeater (processing block 411). In response to the packet, processinglogic determines that the packet is to be sent to the other repeatersand re-broadcasts the received packet to other repeaters (processingblock 412). Then processing logic sends only one copy of the packet tothe rest of the network (processing block 413).

Token-based Receiver Diversity Approach

Note that the above receiver diversity procedure is particularly usefulwhen gigabit or faster Ethernet communication exists between switch 301and repeaters 302 ₁-302 _(n). However, if such is not the case, anothertechnique for receiver diversity may be utilized. For example, atoken-based receiver diversity procedure may be used. In this case,switch 301 has a token for every mobile station on the 802.11 networkand it gives the token to one of the repeaters. In other words, switch301 pre-assigns the token before a packet is even transmitted by amobile station. The repeater stores the token in a table that lists allmobile stations for which it has a token. The repeater with the tokensends the acknowledgement packet to the mobile stations listed in thetable when those mobile stations send packets that are received by therepeater. Therefore, a comparison of received signal strengths forduplicate packets is not necessary. Note that this token basedmechanism, if the repeater with the token does not receive a packetcleanly, but another repeater does, that packet will be forwarded to theswitch and not acknowledged to the mobile client. However, the switchmoves the token before a subsequent packet is sent by mobile station.Therefore, this will only occur for one packet.

In one embodiment, switch 301 includes a database with a listing ofmobile stations and repeater numbers corresponding to the repeater thathas been designated to acknowledge packets received from the mobilestation and, thus, has the token. The table may also include additionalinformation describing the repeater itself.

Since switch 301 receives all packets and their received signalstrength, switch 301 can determine the closest repeater to a particularmobile station. If the repeater determined to be closest to theparticular mobile station is different than the one previouslyidentified as closest, then switch 301 moves the token to a newrepeater, i.e. the one that is closer to the mobile station. The tokenmay be moved on a packet-by-packet basis or every predetermined numberof the packets (e.g., 10 packets, 100 packets, etc.).

Switch 301 may employ a timer to indicate the time during whichduplicate packets may be received in much the same manner the timer isused by the repeaters in the distributed approach described above.

FIG. 4C is a process for managing repeaters using a token-basedmechanism. The process is performed by processing logic that maycomprise hardware (circuitry, dedicated logic, etc.), software (such asis run on a general purpose computer system or a dedicated machine), ora combination of both.

Referring to FIG. 4C, processing logic first determines the location ofmobile stations with respect to repeaters (processing block 451).Processing logic then assigns a token for each of the mobile stations toone of the repeaters (processing block 452) and stores an indication ofthe repeater assigned to each mobile station (processing block 453).This information is stored in a table in memory. In one embodiment, thistable includes a listing of mobile stations and an indication of whichrepeater and/or switch port number is assigned to the mobile station.The table may be the same data structure used for location trackingdescribed below.

In one embodiment, the switch assigns a token by sending an Add Tokencommand to the repeater, which causes the repeater to add a new mobilestation to its table of mobile devices that the repeater supports. Thiscommand includes the MAC address of the mobile station.

Subsequently, processing logic periodically tests whether the repeaterassigned the token for a particular mobile station is still the closestrepeater to that mobile station (processing block 454). If so, then theprocessing is complete. If not, then processing logic moves the token tothe closest repeater (processing block 455) and updates the table toreflect the new repeater that is closest to the mobile station(processing block 456). Processing logic also updates the switch port toreflect the new repeater for use when sending packets to the mobilestation from the switch.

In one embodiment, the switch moves the token by sending a Delete Tokencommand to the repeater that currently has it, causing the repeater todelete the token (and assorted MAC Address) from its list of supportedmobile stations, and by sending an Add Token command to the repeaterthat is currently closest to the mobile station.

FIG. 4D is one embodiment of a token-based process for handling packets.The process is performed by processing logic that may comprise hardware(circuitry, dedicated logic, etc.), software (such as is run on ageneral purpose computer system or a dedicated machine), or acombination of both.

Referring to FIG. 4D, processing logic receives a token from the switch(processing block 470) and stores the token in a table stored in arepeater memory that indicates all the mobile stations for which therepeater has a token (processing block 471).

Subsequently, when processing logic receives a packet from mobilestation (processing block 472), processing logic compares the MACaddress of the 802.11 packet from the mobile station with the address inthe table (processing block 473). At this time, processing logic testswhether the MAC address of a packet equals an address in the table(processing block 474). If so, processing logic provides anacknowledgment (ACK) packet to the mobile station (processing block475). If not, processing logic ignores the packet.

Note that since all repeaters communicate the fact that they received apacket from a mobile station along with the received signal strength toswitch 301, switch 301 is able to determine the coverage area of thetransmission of the mobile station. In one embodiment, each packetreceived by the switch 301 from the repeaters terminates in a networkprocessor in switch 301 (e.g., network processor 1206 of FIG. 12), whichdetermines the coverage area because it has access to the RSSI values.By determining the coverage area of the transmission, switch 301 is ableto track the location of a particular device.

Downstream Communication Scheduling

For communications in the reverse direction (e.g., in the downstreamdirection), in one embodiment, the repeater transmitters are scheduledto reduce collisions. This scheduling is useful because repeaters can beclose enough to interfere with one another. Because of this, switch 301schedules the transmissions to prevent the collisions when the repeatersare actually transmitting.

For example, if a packet is destined for a particular IP address, thenswitch 301 performs an address translation to translate, for example,the IP address into an Ethernet MAC address. Switch 301 uses theEthernet MAC address to search in a location tracking database todetermine which repeater is closest to the mobile station having theEthernet MAC address. Once the repeater is identified by switch 301,then switch 301 knows the switch port on which the packet should be sentso that it is sent to the repeater listed in the location trackingdatabase (for forwarding by the repeater to the mobile station).

Once the repeater (and the port number) has been identified, switch 301checks whether an interference problem would be created if the packet issent by switch 301 to the mobile station at that time. An interferenceproblem would be created if there are other transmissions that would beoccurring when the packet is forwarded onto its destination mobilestation. If no interference problem would exist, switch 301 sends thepacket through the identified port to the repeater most recentlydetermined to be closest to the mobile station. However, if aninterference problem would be created by sending the packet immediately,then switch 301 delays sending the packet through the identified port tothe repeater most recently determined to be closest to the mobilestation.

In one embodiment, to determine if an interference problem would existif a packet is sent immediately upon determining the switch port numberon which the packet is to be sent, switch 301 maintains and uses twodatabases. One of the databases indicates which of the repeatersinterfere with each other during their transmissions. This database isexamined for every downstream packet that is to be sent and switch 301schedules the transmission of downstream packets so that repeaters thatinterfere with each other when they transmit at the same time do nottransmit at the same time. The other database is a listing of mobilestations and the corresponding set of repeaters that last received thetransmissions. If two mobile stations have overlapping sets, then it ispossible for their acknowledgement packets to interfere when theysimultaneously receive non-interfering data packets from differentrepeaters. Because mobile stations send acknowledge packets uponreceiving downstream packets, there is a possibility that mobilestations will interfere with each other when sending theiracknowledgement packets. Switch 301 takes this information into accountduring scheduling and schedules downstream packets to the mobilestations to reduce the occurrence of mobile stations interfering withother when sending acknowledgment packets.

The information in these two databases may be collected by sending outtest packets to the WLAN to determine which repeaters and mobile devicescause the interference described above.

Location—Tracking by Received Signal Strength (RSSI)

FIG. 5A illustrates one technique for location tracking by RSSI.Referring to FIG. 5A, switch 301 obtains the RSSI for each packetreceived by the repeaters and may have multiple RSSI values for a packetwhen that packet is received by two or more different repeaters. Morespecifically, a mobile station communicates with two (or more) repeatersand one repeater is going to have a stronger received signal strengththan the other for the same packet. Based on this information, switch301 is able to determine that a mobile station is closer to one repeaterthan the other. By continually monitoring the received signal strength,switch 301 can track the movement of a mobile station with respect tothe repeaters.

FIG. 5B is a flow diagram of one embodiment of a process for performinglocation tracking by a switch. The process is performed by processinglogic that may comprise hardware (circuitry, dedicated logic, etc.),software (such as is run on a general purpose computer system or adedicated machine), or a combination of both. In one embodiment, theprocessing logic comprises a network processor in the switch (e.g.,network processor 1206 of FIG. 12).

Referring to FIG. 5B, processing logic compares the RSSI for theduplicate packets received by different repeaters from a mobile station(processing block 550) and tests whether the repeater with the highestRSSI for the packet is the repeater listed as closest to the mobilestation in a location tracking table (e.g., database) (processing block551). If not, processing logic updates the table to indicate that therepeater that received the packet with the highest RSSI is the closestrepeater (processing block 552). Processing logic also switches portassignment for the mobile station to the new repeater.

In one embodiment, the location tracking table may include a listing ofmobile stations and their individually assigned repeaters. This tablemay also include, or include instead of the assigned repeater, anindication of the switch port by which the switch is to communicate withthe repeater assigned to each mobile station.

Mobility Supported By Routing

FIG. 6A illustrates mobility supported by routing. Referring to FIG. 6A,the dotted arrow path for communication from switch 301 to mobilestation 601 through repeater 302 ₂ is the original communication pathwith the network. As the mobile station 601 moves, a routing handoffoccurs so that communication occurs over the solid arrowed path. Inorder to accomplish this handoff, switch 301 reroutes the packet to adifferent port. For example, if the first communication path illustratedas the dotted line arrow was on port 1, switch 301 may switch the packetto port 5, the port that associated with the communication path throughrepeater 302 ₀. Thus, mobility is supported by simply moving a packet toa different port of switch 301 that is assigned to a different repeater.In such a situation, the mobility provisions of the 802.11 protocol maybe ignored.

In one embodiment, switch 301 determines that a particular mobilestation is closer to a different repeater (by monitoring the receivedsignal strength of duplicate packets). As described above, switch 301maintains a table (e.g., database) of all mobile stations in the 802.11network and includes an indication of the repeater closest to eachmobile station. Switch 301 performs port-based routing and may use thetable in the same manner an IP routing table is used. Switch 301 has anEthernet port for each repeater. When switch 301 determines that amobile station is closer to a repeater that is different than the onelisted in the database (based on the received signal strength ofduplicate packets among multiple repeaters), then switch 301 updates thedatabase. Thereafter, if a packet is received by switch 301 for thatmobile station, switch 301 merely sends it out on the Ethernet portassigned to the repeater that was most recently determined to be theclosest to that mobile station.

Multi-Switch System

FIG. 7 illustrates one embodiment of a multi-switch system. Referring toFIG. 7, the network architecture includes switches 701 and 702 arecommunicably coupled to server 712. In one embodiment, server 712 ispart of a LAN backbone through which access to the Internet andincorporates other resources made. Alternatively, server 712 may act asan interface to another portion of the communication system. Each ofswitches 701 and 702 is coupled to one or more repeaters in the samemanner as described above with respect to FIG. 3. In still anotherembodiment, server 712 may exist within one of, or both, switches 701and 702.

Protocol Architecture

FIG. 8 illustrates one embodiment of a protocol architecture. Referringto FIG. 8, switch 801 is shown having a network layer 801A and a MAClayer 801B. In one embodiment, the network layer 801A comprises a TCP/IPnetwork layer. MAC sublayer 801B communicates with a MAC sublayer ofeach of repeaters 802 ₁-802 _(N). Thus, in contrast to the prior art inwhich the 802.11 MAC layer is completely within the access point, the802.11 MAC layer is split between switch 301 and repeaters 802 ₁-802_(N), and the MAC sublayer of the repeaters performs much lessfunctionality than the MAC sublayer of the access points describedabove.

In one embodiment, the repeater MAC sublayer is responsible forperforming portions of the 802.11 protocol including handling CSMA/CA,DIFS/EIFS interframe spacing (IFS) timing, SIFS timing and control,beacon frames (during transmit only), generating acknowledgement (ofACK) frames (during transmit only) on data packets received, such as802.11 data frames and generating CTS (clear-to-send) frames in responseto RTS (request-to-send) frames. The repeater MAC sublayer may alsorespond to the resetting of internal network allocation vectors (NAVs)which are embedded into (e.g., RTS and CTS frames). Each of the aboverepeater MAC functions may be implemented in a manner that is well-knownis the art.

In addition to the MAC sublayer, each of repeaters 802 ₁-802 _(N)includes an 802.11 physical layer or other wireless physical layer.

The switch MAC sublayer is responsible for handling multiple frame typesduring reception from the repeaters. In one embodiment, the MAC frametypes the switch is capable of handling include an association request,reassociation request, probe request, ATIM, disassociation,authentication, deauthentication, PS-Pol, CTS (updates NAV inrepeaters), ACK (in response to data frames), data and Null.

The switch MAC frame types that are accommodated during transmissioninclude an association response, a reassociation response, proberesponse, ATIM, disassociation, deauthentication, PS-Pole, data, Nulland RTS (updates NAV in repeater). It should be noted that the MAC frametypes that the switch accommodates during receive and transmit are wellknown in the arts and part of the 802.11 standard. Each of the aboveswitch MAC functions may be implemented in a manner that is well-knownis the art.

FIG. 10 illustrates one embodiment of a hardware architecture for arepeater. Referring to FIG. 10, an RF chip 1002 receives and transmitsRF transmissions using antenna 1003. In one embodiment, RF chip 1002comprises a standard 802.11 RF chip. In one embodiment, antenna 1003comprises a dual-diversity antenna. Communications received by RF chip1002 are forwarded on to baseband processor 1001, which is a digitalchip that is described in further detail below. Similarly, transmissionsto be sent are received by RF chip 1002 from baseband processor 1001.

Baseband processor 1001 is a digital chip that performs the reduced MACfunctions as described above. The repeater also includes a port forcoupling to switch, port 1007. Baseband processor 1001 handlescommunication with switch 301 using this port. In one embodiment, thisport also transfers information through the port at 100 Mb/s bits persecond. Port 107 may also provide power to baseband processor 1001.

A desktop port 1006 may be included to allow desktop or other systems toplug into the repeater. Also, in one embodiment, an LEDs 1005, such asan activity LED, power LED, and/or link LED, may be included in therepeater as well.

FIG. 11 is a block diagram of one embodiment of the baseband processorof a repeater. Baseband processor 1001 includes a repeater MAC andcontrol unit 1105 that interfaces with RF chip 1002 using a protocol. Inone embodiment, the interface comprises a TCP/IP layer and an 802.11 MACsublayer. The repeater MAC/control unit 1105 is coupled to switch 1103.In one embodiment, MAC/control unit 1105 communicates with switch 1103using a TCP/IP layer and an 802.11 MAC sublayer tunneled inside Ethernetpackets. Switch 1103 is also coupled to MAC/PHY layer unit 1104 whichinterfaces the baseband processor to desktop port 1006. Switch 1103 isalso coupled to the activity/power/link LEDs 1005. Similarly switch 1103is coupled to the MAC/physical layer unit 1001 that interfaces the restof the components on baseband processor 1001 to switch port 1007 viaswitch 1103. Also coupled to switch port 1007 is a power distributionunit 1102. In one embodiment, power distribution unit obtains power fromthe CAT5 wiring and provides it to the rest of baseband processor 1001.

FIG. 12 is a block diagram of one embodiment of a switch. Referring toFIG. 12, the switch includes one or more ports 1201 to repeaters 1201.Although 12 are shown, any number may be included. Ports 1201 arecoupled to a switching processor 1202. In one embodiment, switchingprocessor 1202 switches 13 ports of gigabit Ethernet and allowsbroadcast packets to be received on one port and broadcast on the otherswithout involving the rest of the switch. In one embodiment, switchingprocessor 1202 comprises a Broadcom BRCM 5633 gigabit switchingprocessor.

HyperTransport controller 1203 is coupled to switching processor 1202and provides a gigabit ethernet interface to the rest of the switcharchitecture. In one embodiment, the HyperTransport controller 1203includes a diagnostic porthole 1204 and another ethernet port 1205 foruse, for example, coupled to a corporate LAN.

In one embodiment, HyperTransport controller 1203 comprises a GalaileoHyperTransport controller sold by Marvell.

A network processor 1206 is coupled to HyperTransport controller 1203and performs the majority of the functions of the switch, including thereceiver diversity functions and location-tracking functions describedabove, with the exception of the rebroadcast of the broadcast packetsreceived by the switch, which is handled by switching processor 1202. Inone embodiment, network processor 1206 is coupled to a boot memory 1209,a DRAM 1207 and one or more LED's 1208. In one embodiment, networkprocessor 1206 comprises a PMC-Sierra R9000X2 sold by PMC-Sierra, bootmemory 1209 comprises an MB boot flash AMD AM29LV640D boot flash memoryand DRAM 1207 comprises 64 MB synchronous DRAM (SDRAM).

In one embodiment, the network processor 1206 includes a PCI interfaceto a processor 1210. Processor 1210 may host certain applications, suchas, for example, firewall applications. Processor 1210 may perform thesefunctions with the use of hard disk 1211, DRAM 1213 and console port1211. Console port 1211 may provide access to a monitor or keyboard orother peripheral device. In one embodiment, processor 1210 comprises apentium processor manufactured by Intel Corporation of Santa Clara,Calif.

In one embodiment, network processor 1206 executes softwareinstructions, which performs the 802.11 MAC layer. Network processor1206 may also execute a wireless LAN configuration module to configurethe wireless LAN network, a priority traffic administration (e.g.,traffic shaping) module, a management software (e.g., Cisco IOS), asecurity protocol (e.g., 802.1x) module, and a VPN/firewall module.Processor 1210 executes a location tracking module to perform thelocation tracking. Processor 1210 may also execute one or more of thefollowing software modules: clustering/HA, RADIUS/DHCP, sessionmobility, third party applications, XML Web services, useradministration software, and network management software.

Whereas many alterations and modifications of the present invention willno doubt become apparent to a person of ordinary skill in the art afterhaving read the foregoing description, it is to be understood that anyparticular embodiment shown and described by way of illustration is inno way intended to be considered limiting. Therefore, references todetails of various embodiments are not intended to limit the scope ofthe claims which in themselves recite only those features regarded asessential to the invention.

I claim:
 1. A receiver diversity process comprising; each of a pluralityof devices coupled to a switch receiving packets wirelessly transmittedfrom a mobile station; each device of the plurality of devices sendinginformation to other devices in the plurality of devices indicatingwhich of the wirelessly transmitted packets were received by said eachdevice without error and a received signal strength for those packets ofthe wirelessly transmitted packets received without errors; each devicecomparing signal strengths of each packet of the wirelessly transmittedpackets that said each device has received without errors that has alsobeen received by at least one of the other devices in the plurality ofdevices; and in response to the comparison, for each of the wirelesslytransmitted packets received without error, a device having a receivedsignal strength higher than any other of the plurality of devicessending an acknowledgement packet to the mobile station, without havinga remainder of the plurality of devices sending the acknowledgementpacket to the mobile station for the respective wirelessly transmittedpacket.
 2. The process defined in claim 1 wherein each device of theplurality of devices sending information to other devices in theplurality of devices comprises: said each device sending a broadcastpacket to the switch indicating each packet of the wirelesslytransmitted packets received and its received signal strength; and theswitch broadcasting information in the broadcast packet to the otherdevices in the plurality of devices.
 3. The process defined in claim 2wherein the switch receives the broadcast packet on one of a pluralityof ports and wherein the switch broadcasting information in thebroadcast packet to the other devices in the plurality of devicescomprises the switch routing the broadcast packet to ports in theplurality of ports other than the one port.
 4. The process defined inclaim 1 wherein said each device forwarding to a switch each packet ofthe wirelessly transmitted packets comprises said each device sendingsaid each packet via a wired medium.
 5. The process defined in claim 1wherein the wired medium comprises CAT5 wiring.
 6. The process definedin claim 1 wherein the wirelessly transmitted packets are transmittedaccording to the 802.11 family of protocols.
 7. The process defined inclaim 1 wherein each of the plurality of devices comprises repeaters ina wireless local area network (WLAN).
 8. The process defined in claim 1wherein the mobile station in one selected from a group consisting of amobile phone, a cellular phone, a cordless phone, a headset, avoice-enabled mobile station, a laptop computer system, a personaldigital assistant, a computer-data-enabled mobile station, aspeakerphone, video game controller, a DVD controller, a stereocontroller, a TV controller.
 9. A receiver diversity process comprising:a repeater sending information to other repeaters indicating whichwirelessly transmitted packets received by the repeater from a mobilestation without error and a received signal strength for those packetsof the wirelessly transmitted packets received without errors; therepeater receiving information from the other repeaters indicating whichof the wirelessly transmitted packets were received by the otherrepeaters without error and a received signal strength for those packetsof the wirelessly transmitted packets received without errors; therepeater comparing signal strengths of each packet of the wirelesslytransmitted packets that the repeater has received without errors thathas also been received by at least one of the other repeaters; and therepeater sending an acknowledgement packet to the mobile station foreach wirelessly transmitted packet for which the repeater had receivedat a received signal strength higher than any of the other repeaters,without having the other repeaters sending the acknowledgement packet tothe mobile station for the respective wirelessly transmitted packet. 10.The process defined in claim 9 further comprising: the repeater sendinga broadcast packet to the switch indicating each packet of thewirelessly transmitted packets received and its received signalstrength; and the repeater receiving broadcasting information from theswitch indicating each packet of the wirelessly transmitted packetsreceived by the other repeaters and their received signal strength. 11.The process defined in claim 9 wherein the repeater forwards packets tothe switch using a wired medium.
 12. The process defined in claim 11wherein the wired medium comprises CAT5 wiring.
 13. The process definedin claim 9 wherein the wirelessly transmitted packets are transmittedaccording to the 802.11 family of protocols.
 14. The process defined inclaim 9 wherein repeater is part of a wireless local area network(WLAN).
 15. The process defined in claim 9 wherein the mobile stationcomprises is one selected from a group consisting of a mobile phone, acellular phone, a cordless phone, a headset, a voice-enabled mobilestation, a laptop computer system, a personal digital assistant, acomputer-data-enabled mobile station, a video game controller, a DVDcontroller, a stereo controller, a TV controller.
 16. A systemcomprising: a mobile station having a transmitter to transmit packetswirelessly; a plurality of repeaters communicably coupled with themobile station, wherein each of the plurality of repeaters receives oneor more packets of the wirelessly transmitted packets from the mobilestation, wherein each of the plurality of repeaters receives anindication of which of the wirelessly transmitted packets were receivedby other repeaters without error and a received signal strength forthose packets and for each wirelessly transmitted packet receivedwithout error, a repeater having a received signal strength higher thanany other of the plurality of repeaters sending an acknowledgementpacket to the mobile station without having a remainder of the pluralityof repeaters sending the acknowledgement packet to the mobile stationfor the respective wirelessly transmitted packet; and a switch coupledto the plurality of repeaters to receive wirelessly transmitted packetsfrom the plurality of repeaters.
 17. The system defined in claim 16wherein packets are exchanged between the mobile station and theplurality of repeaters using the 802.11 family of protocols.
 18. Thesystem defined in claim 16 wherein one repeater indicates reception of afirst packet from the mobile station without error and signal strengthof the first packet to other repeaters via the switch and comparessignal strength for the first packet with the signal strength of thefirst packet as received by another of the plurality of repeaters todetermine whether the one repeater or said another repeater is to sendan acknowledgement packet to the mobile station.
 19. The process definedin claim 16 wherein the mobile station is one selected from a groupconsisting of a mobile phone, a cellular phone, a cordless phone, aheadset, a voice-enabled mobile station, a laptop computer system, and apersonal digital assistant, a computer-data-enabled mobile station, aspeakerphone, a video game controller, a DVD controller, a stereocontroller, a TV controller.
 20. A method comprising: receiving at leastone 802.11 packet and associated signal strength encapsulated in atleast one Ethernet packet from a first repeater in a wireless local areanetwork (WLAN) via a wired connection; re-broadcasting the at least oneEthernet packet to at least one other repeater for purposes of allowingthe at least one other repeater to compare signal strength of an 802.11packet received by the at least one other repeater with that of aduplicate 802.11 packet received by the first repeater; and one of theat least one other repeater sending an acknowledgment without having thefirst repeater send the acknowledgment in response to determining thesignal strength of the 802.11 packet received by the one other repeateris higher than the signal strength of the duplicate 802.11 packetreceived by the first repeater.